Present day state of the art photochromic eyeglasses have still have numerous serious limitations which have not been properly satisfied even after 40 years or more of photochromic commercialization. The problem is that, when in a form that is clear enough indoors, they never get dark enough outdoors and the switching time of darkening is too slow outdoors and too slow when switching to the clear state indoors. Further, when outdoors and in a high temperature environment the darkening effect becomes reduced. It is well known that the higher the ambient temperature environment the lower the photochromic absorption and or blocking effect.
In addition, photochromics never switch to a dark enough state behind the windshield of a car or other vehicle whereby the windshield filters out ultra-violet wavelengths of light. It is known that photochromic eyeglasses absorb UV light and also in certain cases that of long wavelength blue light.
There has always been a limiting performance balance with photochromatic optics and/or lenses. The balance is the faster the darkening switch outdoors the more sensitive the photochromic optic and/or lens is to ambient heat or high temperature outdoors (which is exacerbated due to the sun's radiation) thus limiting the degree of darkening of the photochromic optic and/or lens and the speed in which it can darken. This is due to once the lens is heated by high outdoor temperatures to a certain level of darkening the lens material softens and the photochromic agent or agents reach a maximum darkening point where they begin to bleach. Embodiments disclosed herein solve this long performance limiting issue of a photochromic optic or lens.
While consumers purchase photochromic eyeglasses the percentage of penetration of photochromics in the US eyeglass market has remained approximately flat and that of approximately 15% to 20% for the last 30 years or more. This is due to both the increased cost of these photochromic eyeglasses and also the serious limitations which have been discussed above. In addition in Europe there has been consumer resistance to photochromic lenses due to the clearing time of the tint when one comes inside from outside.
In addition, other electronic changeable tint devices have also lagged in commercial success and acceptance. Changeable tint liquid crystal devices have met with limited commercial success due to the amount of electrical power needed to drive the devices over a period of time and also the lack of ability to shape post assembly these devices. This is due to most, if not all, changeable tint liquid crystal devices not being electrically bi-stable and in addition once custom shaped after assembly suffering from the liquid crystal leaking out and compromising performance. Finally, changeable tint electro-chromic devices have proven elusive in terms of acceptable performance contrast/dynamic range, ultra-fast switching time and power usage. Thus there is a need for a means to enhance changeable tint devices such to provide for lower power requirements needed to drive the devices, improvement of speed of switching from one color state (transmission of light #1) to another color state (transmission of light #2) and back again (transmission of light #1) and so forth.